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Author Topic: Analog Stage in High End Converters  (Read 4457 times)

Eric Bridenbaker

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Analog Stage in High End Converters
« on: December 10, 2004, 03:27:27 PM »

Hey All,

I've been curious about something lately... looking at the components and design factors that go into high end audiophile gear. This in turn has got me thinking about converters, and what electronics and topologies are currently in use for the analog stage in the various high end converter units.

I'm working on a mic pre now based on the M990 gain block, custom Lundahl amourphous strip core transformers. Absolutely no electrolytic caps. Hard wired with solid core Belden. Stepped gain pot by DACT. Star grounding and power bypass caps located right on the gain block. The design is by Pat Morford. http://www3.telus.net/public/vintage1/kit.htm and is a very minimalist circuit.

I mention this because, after going through the whole unit to ensure that the entire signal path of this preamp is A1, the last thing one would want to do is subject the signal to surface mount electrolytics and tiny IC's in the analog stage of the converter box... SO I'm looking for some advice on two well constructed channels of A/D conversion.

I've heard great things about Dan's converters, also Mytek, Prism, Dcs, Benchmark, Cranesong, Apogee, Meitner, EAR, Weiss. (realizing that there must, or at least should be differences between the $2000 units and the $8000 ones)

Could anyone offer some insight as to what components and topologies go into the design of these units?

Cheers,
Eric



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ammitsboel

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Re: Analog Stage in High End Converters
« Reply #1 on: December 10, 2004, 03:55:49 PM »

Eric Bridenbaker wrote on Fri, 10 December 2004 20:27


I mention this because, after going through the whole unit to ensure that the entire signal path of this preamp is A1, the last thing one would want to do is subject the signal to surface mount electrolytics and tiny IC's in the analog stage of the converter box... SO I'm looking for some advice on two well constructed channels of A/D conversion.


Isn't SMD and IC components a common thing in all Pro Audio converters?
I don't think you can find any at all that doesn't use these parts, including the names you refer to.
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Eric Bridenbaker

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Re: Analog Stage in High End Converters
« Reply #2 on: December 10, 2004, 04:11:37 PM »

ammitsboel wrote on Fri, 10 December 2004 15:55

Eric Bridenbaker wrote on Fri, 10 December 2004 20:27


I mention this because, after going through the whole unit to ensure that the entire signal path of this preamp is A1, the last thing one would want to do is subject the signal to surface mount electrolytics and tiny IC's in the analog stage of the converter box... SO I'm looking for some advice on two well constructed channels of A/D conversion.


Isn't SMD and IC components a common thing in all Pro Audio converters?
I don't think you can find any at all that doesn't use these parts, including the names you refer to.



Thanks Henrick,

Sounds like this is most likely the case. I don't really know anything about converter design, although I'm starting to read a bit about that now on the forum here. Thank You Mr. Lavry!!!

Seems like there are a few common components (IC's) used in most converter designs... although I did just read this (previously posted by Dan in regards to the Lavry Gold):

"Say you want to go beyond what you can find in an IC. Say you want to push new frontiers, what is called state of the art. New concepts, system architecture and ideas not found on an IC (some even incompatible with IC technology) will force you to make a converter from “basic building blocks”. Such “from the ground up” approach requires years of product development. The Lavry Gold converters are such products. They are designed from the ground up. You start with quality resistors and go from there. The design is not the old design with better parts. It is a better design aimed at overcoming the limitations of the old design."

This is the kind of thinking that sounds great.

Cheers,
Eric

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Bob Olhsson

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Re: Analog Stage in High End Converters
« Reply #3 on: December 10, 2004, 04:32:52 PM »

Obtaining a 130 dB dynamic range a quarter inch away from what amounts to a radio transmitter is not trivial! This requires a lot of expertise in power supplies, board design and the interactions between different kinds of components.

Dan Kennedy

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Re: Analog Stage in High End Converters
« Reply #4 on: December 10, 2004, 09:39:47 PM »

Even though the MM opamp is nice and the Lundahl tranny is a good one, don't believe the crap that Pat pushes.

He couldn't design himself into a box, much less out.

Making a circuit that truly does 20 bit performance at audio frequencies is no simple exercise, and getting it to perform properly at higher bit depths is an almost exponentially tougher job.

Pat's hard pressed to do 8 bit work. I know, I've seen it and winced.


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zmix

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Re: Analog Stage in High End Converters
« Reply #5 on: December 10, 2004, 10:16:43 PM »

That 'pre' is truly shocking. Phenolic? point to point?

Anyone who knows anything knows that layout is 99% of design when dealing with off the shelf components. Improving on the performance  of existing monolithics requires knowledge and intuition well beyond what will essentially be a one off prototype.

Dan knows this (Lavry -and- Kennedy).

DIY at this point is sadly relegated to very simple, mid-fi projects.

-CZ

Eric Bridenbaker

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Re: Analog Stage in High End Converters
« Reply #6 on: December 10, 2004, 10:50:40 PM »

Dan Kennedy wrote on Fri, 10 December 2004 21:39

Even though the MM opamp is nice and the Lundahl tranny is a good one, don't believe the crap that Pat pushes.

He couldn't design himself into a box, much less out.

Making a circuit that truly does 20 bit performance at audio frequencies is no simple exercise, and getting it to perform properly at higher bit depths is an almost exponentially tougher job.

Pat's hard pressed to do 8 bit work. I know, I've seen it and winced.





Will keep that in mind -  For someone with engineering experience, good ears, but little design know how, the MM, the lundahls and basically an API 312 circuit topology seemed like a pretty good starting point. Hoping he's got this one right.

zmix wrote on Fri, 10 December 2004 22:16

That 'pre' is truly shocking. Phenolic? point to point?

Anyone who knows anything knows that layout is 99% of design when dealing with off the shelf components. Improving on the performance  of existing monolithics requires knowledge and intuition well beyond what will essentially be a one off prototype.

Dan knows this (Lavry -and- Kennedy).

DIY at this point is sadly relegated to very simple, mid-fi projects.

-CZ


Yep, that would seem to be the case, directly attaching the components with the wire, using the breadboard as a mount. Will need to get a peek at how the 312's are laid out, this will probably help.

Since the kit came a year ago,it's been hard for me to track down the parts and find time to complete the project. All in all, the experience has forced me to do some reading into basic electronics, and gain a better understanding of the the gear. It has also induced a certain level of respect for the audio designers here and everywhere.

Cheers,
Eric
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